69 Smog pump diverter valve
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69 Smog pump diverter valve
My 69 L71's smog pump diverter valve's diaphragm is shot, not holding any vacuum. Besides paying for an expensive restoration, is there a cheaper equivalent replacement diverter valve that will work?
I have all the original parts and they will be restored in the future, but right now I just want a working smog system.
I have all the original parts and they will be restored in the future, but right now I just want a working smog system.
Last edited by cwwhk; May 17, 2014 at 11:29 AM.
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From: Charlotte NC
My 69 L71's smog pump diverter valve's diaphragm is shot, not holding any vacuum. Besides paying for an expensive restoration, is there a cheaper equivalent replacement diverter valve that will work?
I have all the original parts and they will be restored in the future, but right now I just want a working smog system.
I have all the original parts and they will be restored in the future, but right now I just want a working smog system.
DUB
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From: BC
I have the same problem with my 69 L36. Is the diaphragm supposed to to hold a continuous vacuum or does it bleed off? My valve still works but loses vacuum right away with a vacuum tester attached. Would like to figure out a way to replace this without spending 500 bucks. Or more....
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Searched high and low on the internet, but it seems a correct and inexpensive solution is not possible.
Contacted Bill Hodel. Contrary to what I read Bill said the last time he rebuilt diverter valves for a 69 L71 was 10 years ago. I decided I will buy a NOS diverter valve as well as a pair of check valves from him. Not cheap but hopefully this will solve my problem.
Contacted Bill Hodel. Contrary to what I read Bill said the last time he rebuilt diverter valves for a 69 L71 was 10 years ago. I decided I will buy a NOS diverter valve as well as a pair of check valves from him. Not cheap but hopefully this will solve my problem.
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From: BC
I had another look at mine today. With the diaphragm leaking the valve remains in the default or open position so the system is working at all times. I don't see anything wrong with this as all the diverter does is block pressure at the pump in a high vacuum situation like idle but has nothing to do with engine vacuum except for the signal. Plus, my vacuum at idle went from 17 to 19 inches because of the diaphragm leak. Re-tuned the carb, checked timing for the vacuum diff at idle and good to go.
My question is why would GM not want the system working at high vacuum conditions when the pump is run off a belt and is working at all times anyway? Why the diverter valve?
My question is why would GM not want the system working at high vacuum conditions when the pump is run off a belt and is working at all times anyway? Why the diverter valve?
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I think you've got it backwards. The AIR system works with high vacuum conditions but not with low.
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From: BC
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Yes, you're right. I had my theory backwards. As for why the diverter valve is there:
"Carbureted engines' exhaust raw fuel content tends to spike when the driver suddenly releases the throttle. To prevent the startling and potentially damaging effects of the explosive combustion of this raw fuel, a diverter valve is used. This valve senses the sharp increase in intake manifold vacuum resulting from the sudden closure of the throttle, and diverts the air pump's outlet to atmosphere. Usually this diverted air is routed to the engine air cleaner or to a separate silencer to muffle objectionable pump noise."
http://en.wikipedia.org/wiki/Secondary_air_injection
"Carbureted engines' exhaust raw fuel content tends to spike when the driver suddenly releases the throttle. To prevent the startling and potentially damaging effects of the explosive combustion of this raw fuel, a diverter valve is used. This valve senses the sharp increase in intake manifold vacuum resulting from the sudden closure of the throttle, and diverts the air pump's outlet to atmosphere. Usually this diverted air is routed to the engine air cleaner or to a separate silencer to muffle objectionable pump noise."
http://en.wikipedia.org/wiki/Secondary_air_injection
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From: BC
For the last 45 years I thought the diverter valve opened the flow from the pump but it closes it. No idea why the valve is even there. The pump runs full time so the valve doesn't even do much and runs nice and steady with no goofy pump noises like ball bearings in a can when you drop off the gas or at a steady rpm in a low gear.
My point is, I can see the pump but why the diverter?
My point is, I can see the pump but why the diverter?
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From: BC
Ah.. I got it.
High rpm and drop off the gas...
If the diverter valve didn't open from high engine vacuum on carb closure you could blow a hose off the A.I.R. or a pump gasket from pressurization with the pump running at high speed.
High rpm and drop off the gas...
If the diverter valve didn't open from high engine vacuum on carb closure you could blow a hose off the A.I.R. or a pump gasket from pressurization with the pump running at high speed.
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A leaky diverter valve diaphragm means air is getting into the intake manifold thus upsetting the air/fuel ratio. Not good IMHO.
From what I have read, diverter valve dumps the air through the muffler port to prevent backfire in the exhaust on sudden closing of throttle.
From what I have read, diverter valve dumps the air through the muffler port to prevent backfire in the exhaust on sudden closing of throttle.
Last edited by cwwhk; May 20, 2014 at 03:37 AM. Reason: Clarity
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After 11 months of procrastination, I finally installed the smog system back on the car.
Still need to rebuild my original pump so temporarily using a remanufactured pump with black front plastic fan. Rest of the smog system is either correct NOS or original parts from the car.
And yes the unburnt fuel smell at idle is much less noticeable now with the smog pump.
Anybody know the correct procedure to pull off the white front plastic pump fan without damage so I can get to the front bearing to replace or repack?
Still need to rebuild my original pump so temporarily using a remanufactured pump with black front plastic fan. Rest of the smog system is either correct NOS or original parts from the car.
And yes the unburnt fuel smell at idle is much less noticeable now with the smog pump.
Anybody know the correct procedure to pull off the white front plastic pump fan without damage so I can get to the front bearing to replace or repack?
Last edited by cwwhk; May 22, 2015 at 08:58 AM.
Drifting
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Let the procrastination end. Hope you are still happy with the car.
Just got my Aug. 2015 issue of Vette Magazine and it has a long article on parts and functions of the air injection system. You may already know most of this, but I thought I would mention it. Not sure if you have access to magazine, but maybe it is available on the web.
Take care. Ralph
Just got my Aug. 2015 issue of Vette Magazine and it has a long article on parts and functions of the air injection system. You may already know most of this, but I thought I would mention it. Not sure if you have access to magazine, but maybe it is available on the web.
Take care. Ralph
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Let the procrastination end. Hope you are still happy with the car.
Just got my Aug. 2015 issue of Vette Magazine and it has a long article on parts and functions of the air injection system. You may already know most of this, but I thought I would mention it. Not sure if you have access to magazine, but maybe it is available on the web.
Take care. Ralph
Just got my Aug. 2015 issue of Vette Magazine and it has a long article on parts and functions of the air injection system. You may already know most of this, but I thought I would mention it. Not sure if you have access to magazine, but maybe it is available on the web.
Take care. Ralph
Drove the car only once. Happy with the car every time I look at it.
Regards,
Wayne